Fixed stroke piston machines with improved counterbalancing and driving mechanism

ABSTRACT

Counterbalanced fixed stroke piston machines are shown in which first and second movable slider and counterbalancer members are interconnected by a special counterbalancing and driving mechanism for straight-line, reciprocating movement in opposite directions from each other along a common longitudinal axis at all times. The machines include a counterbalanced single-throw crankshaft having a crank portion and a counterbalancing portion. A connecting rod has one end pivoted to the crank portion and the other end connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other. The machines include one or more piston portions associated with and reciprocating longitudinally as a unit with one or both of the slider and counterbalance members, together with power means for applying a driving force to one of the crankshaft, slider and counterbalancer members. The special interconnecting mechanism includes at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically around the outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally with one of the slider and counterbalancer members and having at least two racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and at least two outer racks reciprocating longitudinally with the other of said slider and counterbalancing members, said outer racks being spaced outwardly from and parallel to the inner rack portions and having teeth projecting inwardly and respectively engaging the corresponding gear members, and a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis. In a preferred embodiment, the power means consists of a rotary driving connection on the crankshaft member, and the machine is a two-chamber compressor in which two cylinder aand two piston portions provide two compression chambers along the same longitudinal axis. A variety of design possiblities are disclosed.

United States Patent [191 Braun 1 1 FIXED STROKE PISTON MACHINES WITH IMPROVED COUNTERBALANCING AND DRIVING MECHANISM [75] Inventor: Anton Braun, Minneapolis; Oswald Thun, Reeklinghausen, both of Minn.

[73] Assigne e: Anton Braun, Minneapolis, Minn.

[22] Filed: Apr. 30, 1973 [21] Appl. No.: 355,750

[52] U.S. Cl. 74/44 [51] Int. Cl. Fl6h 21/27 [58] Field of Search 308/3 CH; 74/44, 29;

[56'] 3 References Cited UNITED STATES PATENTS 1,399,666 12/1921 Short. 123/56 AC 1,433,649 10/1922 Powell 74/44 1,581,439 4/1926 Gray 74/29 1,841,021 1/1932 Everts 123/56 AC 2,156,010 4/1939 Connor 123/56 AC FOREIGN PATENTS OR APPLICATIONS 417,470 8/1925 Germany 74/44 Primary ExaminerWesley S. Ratliff, Jr. Attorney, Agent, or Firm-Dorsey, Marquart, Windhorst, West & Halladay ABSTRACT Counterbalanced fixed stroke piston machines are shown in which first and second movable slider and counterbalancer members are interconnected by a special counterbalancing and driving mechanism for straight-line, reciprocating movement in opposite directions from each other along a common longitudinal axis at all times. The machines include a counterbalanced single-throw crankshaft having a crank portion and a counterbalancing portion. A connecting rod has one end pivoted to the crank portion and the other [451 Jan. 21, 1975 end connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other. The machines include one or more piston portions associated with and reciprocating longitudinally as a unit with one or both of the slider and counterbalance members, together with power means for applying a driving force to one of the crankshaft, slider and counterbalancer members.

The special interconnecting mechanism includes at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically around the outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally with one of the slider and counterbalancer members and having at least two racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and at least two outer racks reciprocating longitudinally with the other of said slider and counterbalancing members, said outer racks being spaced outwardly from and parallel to the inner rack portions and having teeth projecting inwardly and respectively engaging the corresponding gear members, and a frame member moving as a unit with said outer racks and rigidly interconnecting said outerracks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis.

1 In a preferred embodiment, the power means consists 18 Claims, 6 Drawing Figures PATENIED JANZI I975 SHEET 1 OF 2 l II PATENTED JAN21 I975 SHEET 2 OF 2 FIXED STROKE PISTON MACHINES WITH IMPROVED COUNTERBALANCING AND DRIVING MECHANISM BACKGROUND OF THE INVENTION Various fixed stroke piston machines are known in the prior art in which a crankshaft is connected by one or more connecting rods to one or more reciprocating piston members, in order to transmit or convert rotary motion from the crankshaft to reciprocating motion of such piston members, or vice-versa. Various arrangements have also been proposed for counterbalancing these and other machines to varying degrees. In some cases, the desired degree of balance has been sought by the provision of multiple-throw crankshafts, with a number of crank portions arranged at different angles around the crankshaft axis. In other cases a single crank or different crank portions have been joined by appropriate connecting rods to a plurality of different reciprocating pistons which may move on two or more different axes extending at different angles from the crankshaft axis.

In the particular class of fixed stroke piston machines which involve single-throw crankshafts, attempts have been made to provide the necessary balance by appro priate counterbalancing portions at different points on a crankshaft, so. that the crankshaft counterweights will partly balance both the rotary moving masses of the crank itself and the longitudinally reciprocating masses of the connected reciprocating member or piston.

A discussion of the prior art constructions and problems and one example of an effort to achieve balance in a single-throw crankshaft engine are shown, for example in U.S. Pat. No. 3,415,237 ofJ.R. I-larkness. As discussed-therein, efforts to balance piston reciprocation by providing a crankshaft with a counterbalancing weight portion, disposed 180 opposite the crank portion to which one end of the piston connecting rod is attached, would require sufficient counterbalancing weight or mass to substantially overbalance the crank itself and the attached end of the connecting rod. Hence, there is a resulting centrifugal force vector diametrically opposite the crank. Thus, Harkness points out that ithas not been practical to achieve substantially complete counterbalancing of both the reciprocating piston and of the rotary crank portion, and that engines or devices of this single-throw type have been counterbalanced just enough to achieve a limited condition of overbalance from a rotary standpoint, and incomplete balancing of the reciprocating forces. Harkness proposed to solve this problem by using two contra-rotating counterbalances which are so arranged that they reduce the centrifugal forces which would otherwise be added by the rotation of such masses and in effect provide a 100 percent overbalance of the reciprocating piston parts.

The solution proposed by Harkness, however, does add substantial additional rotary masses and requires additional gearing and parts in connection with the crankshaft construction. Moreover, the I-Iarkness proposal involves the addition of a balancing mechanism to a crankshaft, without in any way modifying the normal direct connection between the crankshaft and the reciprocating piston.-

There has been at least one disclosure of an effort to counterbalance heavy reciprocating parts in other types of crankshaft driven machines, such as crank and punch presses or embossing machines, by the use of a separate counterbalancing unit, in which a crankshaft drives a reciprocating member through a connecting rod, and the reciprocating member is connected in turn, by individual pivotally mounted levers, to each of a pair of spaced apart counterweights which are located at opposite sides of the reciprocating member. In that case, the arrangement of counterweights and their drive is said to be completely isolated from the main crank assembly of the main machine which has the heavy reciprocating parts to be counterbalanced. Such disclosure does not show the manner in which the separate counterbalancing unit is to be connected to such a main machine or what the total combination of elements would be. It seems clear, however, that such a proposal involves the addition or connection of something to a main machine or its crankshaft without any suggestion for modification of whatever direct connection the machine normally includes between its main crank assembly and its heavy reciprocating press or embossing machine parts, and without any suggestion for modifying or adding to the reciprocating machine parts which are driven by such a main crank assembly. In the field of variable-stroke piston machines, such as free piston engines, various synchronizing and balancing devices have also been used, one particularly advantageous form being shown in US. Pat. No. 3,524,436 of Anton Braun. Such free-piston engines, however, do not involve rotary crankshafts which rotate through successive complete revolutions of 360 in the same direction, as is the case in fixed-stroke machines. Thus, such variable-stroke machines have been considered as a separate class with its own special problems to solve. One does not normally look to that class for solutions to the special problems of another class, nor would one find in said Braun patent any teaching as to how and where a synchronizing apparatus as disclosed therein for variable-stroke free piston engines might be combined as part of 'a novel counterbalanced driving mechanism for fixed-stroke piston machines.

SUMMARY OF THE INVENTION The present invention provides an improved counterbalanced fixed stroke piston machine having a first movable slider member supported for reciprocating straight-line movement with its center of gravity moving along a desired longitudinal axis, a counterbalanced single-throw rotary crankshaft with both a crank portion and a counterbalancing portion, a connecting rod having one end pivotally connected to the slider member and the other end pivotally connected to the crank on the crankshaft for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the-other, and a second movable member serving as a counterbalancer member also adapted for reciprocating straight-like movement with its center of gravity moving alongthe same desired longitudinal axis, together with a special interconnecting mechanism for connecting the first and second movable members to each other for counterbalancing straight-line movement of such members in opposite directions to each other along said axis at all times. At least one piston portion is associated with and reciprocates longitudinally as a unit with one of the first and second movable slider and counterbalancer members, and the machine includespower means for applying a driving force to one of the crankshaft, slider and counterbalancer members.

The special interconnecting mechanism between the first and second movable slider and counterbalancer members includes at least two oscillating gear members supported for rotation on supporting axes extending generally cross-wise of said longitudinal axis and spaced symmetrically from each other around and outwardly from such axis, an inner rack portion reciprocating longitudinally as a unit with one of said slider and counterbalancer members, said inner rack portion having at least two inner racks with teeth projecting outwardly-away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement longitudinally between the gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said slider and counterbalancer members, said outer racks being spaced outwardly from and parallel to the respective inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along saidlongitudinal axis. Thus the outer racks are guided in such a way that, with the special and rigid interconnection of the outer racks and the frame member, the outer racks are constrained against lateral outward separation due to the force components normal (i.e., perpendicular) to that axis resulting from the driving engagement between the outer racks and corresponding gear members, while at the same time allowing the racks to float freely within the small limits of the unavoidable tooth errors and thusly drastically reducing the substantial dynamic tooth loads usually resulting from these tooth errors. This allows greatly reduced rack and gear sizes. The rotary gear members are spaced longitudinally from the pivotal connection between the connecting rod and the slider member, and the particular rack portion which reciprocates longitudinally as a unit with the slider member is preferably a separate member which has a pivotal connection to the slider member for limited pivotal movement on a crosswise axis.

The combination and location of this special interconnecting mechanism with a single-throw counterbalanced crankshaft and a connecting rod pivoted to both the crank and the slider member provides an improved counterbalancing and driving mechanism for fixed stroke piston machines. For optimum balancing, the mass of the counterbalancing member, including all portions moving longitudinally as a unit therewith, exceeds the mass of the first movable member, including all portions other than the connecting rod moving longitudinally as a unit therewith, by an amount equal to only a portion of the total connecting rod mass, and the effective mass of the counterbalancing portion of the crankshaft exceeds the mass required to counterbalance only the single-throw crank portion by an amount equal to only a portion of the mass required to balance the total connecting rod mass.

In some embodiments of the invention, a piston portion moves as a unit with the movable slider member. In other cases a piston portion moves as a unit with the movable counterbalancer member. In still other cases, at least one piston member moves as a unit with each of the slider and counterbalancer members. Thus a piston portion having at least one piston face can move longitudinally as a unit as at least part of one or both of the slider and counterbalancer members or assemblies. Such a piston portion may even serve as substantially an entire slider or counterbalancer member.

In a preferred embodiment, the power means consists of a rotary driving connection on the crankshaft member, and the machine is a two-chamber compressor in which two cylinder wall portions and two piston portions provide two compression chambers along the same longitudinal axis. The two cylinder wall portions may be parts of separate cylinders or of a common cylinder, and the two piston portions may be separate pistons or parts of a common piston member of uniform or stepped cross section.

In another specific embodiment of the invention, at least two piston members are provided which are spaced longitudinally at opposite sides of the crankshaft, with one piston serving as the slider member, with the other piston moving as a unit with the first piston, and with the counterbalancer member on the opposite side of the crankshaft from the piston serving as a slider member. Thus, the invention provides substantial design freedom in the selection of different relative axial locations for the respective crankshaft, slider and counterbalancer members and for the various piston portions and plural compression chambers.

Other features, variations and embodiments of the invention will be apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWING In the drawings which form a part of this application, and in which like reference characters indicate like parts:

FIG. 1 is a schematic view of one form of fixed stroke piston machine embodying the special counterbalancing and driving mechanism according to the invention, in which inner and outer racks and corresponding intermediate oscillating gears interconnect respective slider and counterbalancer members, with the outer racks rigidly connected to each other and pivotally connected to the slider member for longitudinal movement as a unit with such member;

FIG. 2 is a sectional view on the line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 1 of another embodiment in which an inner-rack member is pivotally connected to the slider member and the outer racks are a part of a counterbalancing member;

FIG. 4 is a view similar to FIG. 1 of an embodiment in which a rotary crankshaft is located between the point of pivotal connection of the connecting rod to the slider member and the axial longitudinal location of the inner and outer rack members and counterbalancer member;

FIG. 5 is a partially schematic view of a two-chamber compressor assembly embodying the special counterbalancing and driving mechanism of this invention, in which the respective compressor chambers are longitudinally spaced on opposite sides of a driving crankshaft, and in which the slider member reciprocates as a unit with two piston members, one in each chamber, and the counterbalancing member provides only a counterbalancing function at a location spaced longitudinally between the driving crankshaft and one of the pistons; and

FIG. 6 is a view similar to FIG. 5 of another embodiment of the invention in which a balanced twochamber compressor assembly includes a single piston member with two opposite working faces which divide a single compressor cylinder section into two compressor chambers, and in which the piston member serves as the slider member and is driven directly by a connecting rod from a rotary driveshaft spaced longitudinally at one side of the piston member, while the movable counterbalancer member is spaced longitudinally at the other. side of the combination piston and slider member at a location longitudinally beyond the compressor cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS --nected to crank 71 through a connecting rod 67 which has one end 69 pivoted to crank 71 on the counterbalanced crankshaft 72 and its other end 68 pivoted at 57 to the slider 58. Crankshaft 72 has a counterbalancing portion 75 with its effective center of mass angularly spaced 180 from the single-throw, crank 71. Moving longitudinally asa unit with slider member 58 is a first portion of the counterbalancing and driving mechanism which interconnects the slider member 58 and an oppositely moving second movable'member serving as a counterbalancing member, which includes at least a shaft 29. This first portion of the interconnecting mechanism includes an outer rack portion having outer racks 48 and 49 which are rigidly connected to each other by frame or wall members 51 and 52 (see FIG. 2) and which are connected to the slider member 58 by extensions or plates 56 and shaft 57.

Frame members 51 and 52 provide a rigid connection between the outer racks 48 and 49 at a location immediately adjacent and along side two rotary or oscillating gear members 34 and 36, which are supported for rotation on supporting shafts or axes 37 and 38 extending generally transversely of the longitudinal axisof movement of the slider 58 and counterbalanc'er 29. The rigid frame member construction provided by front and rear connecting plates, 52 and 51 respectively, provide a rigid frame member construction, such that any force tending to move rack 48 to the left as viewed in FIG. 1 (for example, by engagement of the teeth of member 34 with the teethof rack 48) will be neutralized or counterbalanced by the engagement between the oppositely projecting teeth of the other outer rack 49 with the outwardly projecting teeth of the other gearmember 36. Thus the respective racks 48 and 49 have a sort of floating supporting engagement with the gears (e.g., pinions) 34 and 36 and do not require frictional supporting engagement with the inner surfaces of the cylinder or housing wall 42. On the contrary, a definite spacing is provided between such racks and the housing, as clearly shown in FIG. 2, to provide the desired freedom of movement and floating support.

As further shown in FIGS. 1 and 2, the connecting plates or walls 51 and 52 are provided with appropriate longitudinal slots 53 to permit longitudinal reciprocating movement of the walls and associated rack members with respect to the supporting shafts 37 and 38 which extend outwardly beyond therespective connecting plates 51 and 52 into suitable cross-beam supports 39 and 41 (FIG. 2).

Thus the pinion supporting shafts 37 and 38 are carried in suitable openings in the front and rear crossbeams 39 and 41, which extend across from one side of the housing wall or frame to the other. The housing wall 42 was further provided with appropriately located openings 54 in alignment with pinion shafts 37 and 38, so that these shafts can bereadily inserted or removed during assembly or disassembly of the interconnecting mechanism which includes the various racks and the interconnecting gear members 34 and 36.

This interconnecting mechanism further includes an inner rack portion 30 at the lower end of longitudinally reciprocating rod 29, which is specifically illustrated as a double rack having two oppositely and outwardly directed toothed racks 32 and 33, which respectively engage the inwardly projecting teeth of the two laterally spaced gear members 34 and 36.

The construction of this counterbalancing and driving mechanism is such that the respective inner and outer rack portions, and the particular slider and counterbalancing members which are associated with an move longitudinally as a unit as at least part of such rack portions always move in exactly opposite longitudinal directions along the longitudinal axis of the machine and in equal increments of distance at each instant during operation of the machine.

At least one piston portion with at least one working face serving as a working or power member may be associated with either or both of the slider member 58 and counterbalancing member 29, as shown for example in dotted outline at 102 and 103, respectively. If member 102 or 103 is selected as a piston portion for the piston machine, then the appropriate cylinder portion 104 may include suitable valves, parts or other necessary elements.

In FIG. 1, member 102 is shown schematically as a piston with an upper piston face 102a, and is connected by shafts or extensions 46 and 47 to the outer rack portion and its wall members 51, 52. Member 103 is also shown schematicallyas a piston in FIG. 1, with piston faces 103a and 103b, all secured to shaft 29 for longitudinal movement as a unit.

When members 102 and 103 are selected as piston portions, the space between them can serve as a compressing chamber 17 in which the piston faces 102a and I 10312 serve as the lower and upper walls of the compressor chamber and always move in opposite directions through the action of the interconnecting mechanism described. If a two-chamber compressor is needed, the space 18 above upper piston face 103a may be closed by a suitable cylinder head to provide the desired second compressor chamber. Thus, the specific arrangement shown schematically in FIG. 1 provides a piston or working member moving longitudi-' nally as a unit with each of the slider and counterbalancer members.

Other types of working members can also be used, and it will be understood that the balancing and driving mechanism shown essentially in heavy lines in FIG. 1 may transmit driving forces in either direction, i.e., from drive shaft 72 to one or more driven members 102 or 103, or from one -or more reciprocating driving members 102 or 103 to rotary driven shaft 72. In either case, the balanced driving mechanism is adapted to counterbalance in appropriate fashion both the longitu dinal and rotary components involved. The longitudinal components are particularly and precisely balanced by supporting the slider member 58, the counterbalancer 29, and their respective associated parts for straight-line reciprocating movement at all times in respectively opposite directions. Furthermore, the respective masses associated with each of the slider and counterbalancer members are made equal to each other, taking into account an appropriate portion of the mass of the swinging connecting rod 67.

In effect, the total mass of the counterbalancer-member and its associated parts, exceeds the total mass of the slider member, plus all its parts except the connecting rod, by an amount equal to only a portion of the connecting rod mass. Also, the effective mass of the counterbalancing portion, i.e. the effective off-center mass which is available to counterbalance the crank portion, exceeds the mass required to balance only the mass of the crank portion by an amount equal to only a portion of the mass required to balance the total connecting rod mass. In an ideal case, the common center of mass of all parts of the piston machine and its driving mechanism should thus remain at essentially a fixed location along the longitudinal axis of movement of the slider and counterbalancer members. As a practical matter, however, some variation from the ideal may be acceptable, or even necessary, depending on the particular shape, dimensions and mass of the swinging connecting rod, for example.

Another embodiment of a balanced driving mechanism according to the invention is shown at 106 in FIG. 3. Here the slider member 58 is connected to a rotary counterbalanced crankshaft 72, just as in the previous embodiment, and the interconnecting mechanism between the slider member 58 and a suitable counterbalancer member is again provided by respective inner and outer rack portions engaging the rotatable gears 34 and 36. In this case, however, the inner rack portions 32 and 33, which engage the inner teeth of rotating pinions 34 and 36, are carried by a central longitudinally movable shaft 107, has its lower end 108 pivotally secured to the cross shaft 57 of slider 58. This pivotal connection permits the rack portion 32 and 33 to have some limited floating support or guidance at 34 and 36, while moving essentially as an integral unit longitudinally with the slider member 58. The upper end 109 of central shaft 107 may be connected to a suitable working or power member for straight-line reciprocation with slider member 58.

In this embodiment, the outer rack portions 48 and 49 and associated plates, such as 51, serve as at least part of the counterbalancer member, as to which the total mass of all associated parts is designed to exactly counterbalance, by straight-line longitudinal movement at all times in opposite directions, the straight-line movement ofthe slider member 58, shaft 107 and their associated parts, including only a portion of the connecting rod mass.

A specific form of balanced driving mechanism according to the invention is further illustrated at 111 in FIG. 4. Here the connecting rod 67 again connects the crank 71 on counterbalanced crankshaft 71 to the vertically or longitudinally movable slider 58 which has guiding surfaces 59 and 61 insuring straight-line reciprocating movement of the slider. In this embodiment,

the rotating pinions 34 and 36 and the respective inner and outer toothed racks which provide the interconnecting mechanism between the slider member and counterbalancer member are located at the opposite side of crankshaft 72 from slider member 58. Thus, rigid connecting members 112 and 113 extend from slider member 58 past the crankshaft 72 to the outer rack members 48 and 49 and their associated frame members, such as 51. In this case the inner rack member 30 and its associated counterbalancer member 29 are oriented so that rod 29 extends away from shaft 72 on the opposite side of the shaft from slider 58. Thus it is possible to provide one or more working or power members, as shown schematically in dotted outline at 114 and 116 for movement as a unitary portion of the respective slider member 58 and counterbalancer member 29. Thus a particularly compact arrangement is obtained in which oppositely moving reciprocating members 114 and 116 can be positioned at opposite sides of a crankshaft 72 for opposed operation to achieve a desired out of phase operating function.

The driving mechanism shown in FIG. 4 is particularly adaptable to a two-stage compressor assembly 117 as shown in FIG. 5. In this embodiment, the counterbalanced crankshaft 77 is carried in a frame or housing 121 which is positioned generally horizontally. For convenience, this housing may be supported on the top of the driving motor 77 by an intermediate frame 119, which motor 77 is supported in turn by an appropriate base of pedestal 118. motor 77 drives shaft 72 by a belt connection 74 between drive pulley 76 and driven pulley 73. Regardless of the relative location of motor 77, however, the compressor assembly 117 includes a first compressor cylinder 122 at the tight end, as viewed in FIG. 5. Cylinger 122 provides a first compression chamber 123 in which a piston 124 moves back and forth for straight-line reciprocating movement along a longitudinal horizontal path. In this case piston 124 serves as the slider member according to the present invention and is connected to and driven through the connecting rod 67, which has one end 68 pivoted to cross shaft 126 in the combination piston and slider member 124. Compressor chamber 123 has an inlet valve 127 and an outlet valve 128 of known constructron.

The compressor assembly 117 includes a second compressor cylinder 129 at the opposite end of the assembly from cylinder 122. Thus cylinder 129 provides a second compressor chamber 131 in which a second longitudinally movable piston 132 provides the desired compressor function. Piston 132 also constitutes part of the slider member assembly and is secured by central shaft 133, cross-bar or yoke portion 137, and upper and lower rigid connection rods 138 and 139 to the first compressor piston 124, so that all of these parts move back and forth on a straight line as a unit.

In this case, connecting shaft portion 133 carries inner racks 134 and 136 which engage the inner teeth of intermediate gears 34 and 36 supported in the frame 121 in the same manner previously described. Also in thise case a counterbalancer member indicated generally at 141 includes outer racks 48 and 49, as in the previous embodiments, which engage the outer teeth of pinions 34 and 36, and which are secured to each other by frame or wall members 51 and 52 in rigid manner, similar to that shown in FIG. 2, so that the counterbalancer member 141 is guided by thepinions 34 and 36 in a floating type of support, with no frictional engagement between the counterbalancing member and the stationary portions of housing 121 and with a definite spacing between such parts.

The embodiment of FIG. has the particular advantage that the respective compressor cylinders 122 and 129 are located at opposite ends of the assembly and that standard compressor cylinders and cylinder heads of existing construction can be readily obtained in desired sizes and secured at the ends of the assembly to provide a wide variety of design possibilities for different applications. Thus, all portions of the balanced driving mechanism, including the counterbalanced rotary crankshaft 72 and the respective slider and counterbalancer members are located in the central or intermediate portions of the assembly, while the respective compressor cylinders,including the inlet 127 and outlet 128 of compressor cylinder 122, and the inlet 142 and outlet 143 of compressor cylinder l29'are at the outer ends of the assembly and readily accessible for replacement or repair.

Another balanced, two-chamber compressor according to the invention is shown generally at 144 in FIG. 6. In this case the slider member 146 has a cross shaft 147 which is pivotally connected to the upper end of connecting rod 67 for reciprocation of slider member 146 in response to rotary movement of the counterbalanced crankshaft 72. The slider member in this case consists of at least the skirt portion of a stepped piston, which is guided for straight-line reciprocating movethem within a cylindrical housing portion 148 of the assembly. Piston 149 has an upper face 151 and an annular outer lower face portion 152 and moved longitudinally within cylinder 153 to divide the cylinder into an upper first'compressor chamber 154 and a second or lower compressor chamber 156. The upper chamber has an inlet-valve 157 and an outlet valve 158. The outlet valve is connected through a suitable intercooler 159 to the inlet valve 161 of the second compressor chamber. The outlet valve 162 from the second chamber 156 communicates with a delivery conduit 163 which delivers the compressed fluid to a receiver 164, from which it may be withdrawn, as needed, through an outlet 166 controlled by a suitable valve mechanism (not shown).

In this case the piston or working member 149, and the stepped arrangement shown in FIG. 6, are suitable for use of chamber 154 as a first-stage compression chamber, while chamber 156 serves as a second-stage compressor.

The desired longitudinal counterbalancing of slider member 146 and its associated piston portion 149 isprovided by a mechanism located above the cylinder head. Thus a connecting shaft 167 has its lower end rigidly fixed at 168 to piston 149 and projects upwardly through a seal 169 in a central opening 171 of the cylinder head into an upper housing section 172 for the counterbalancer member. The upper end of shaft 167 is provided with a double rack portion including the inner racks 32 and 33, which engage the inner teeth of pinions 34 and 36 supported on transverse shafts at a fixed location in housing 172. In this case the counterbalancer member is indicated generally at 173 and includes two outer rack portions 48 and 49 secured together by frame members such as 51, which extend between and rigidly interconnect the racks immediately adjacent gears 34 and 36, just as in the other embodiments of the invention. Thus the combination of the outer racks and associated frame members should have sufficient mass to perform a counterbalancing function for the assembly, since no other working member is associated to move as a part of the counterbalancer member in this example.

The counterbalanced fixed stroke piston machines and the improved counterbalancing and driving mechanisms for such machines, as described in the foregoing specification arebelieved to offer advantages in both flexibility of design and construction and the possibility of using standardized individual elements in some cases, such as available ranges of compressor cylinders and pistons and the like, which can be configurations in various configuration to meet the requirements of different applications. The improved balancing and interconnecting mechanism with inner and outer racks engaging intermediate rotary pinions for insuring equal and oppositely directed (i.e. one-to-one) straight-line movements of the slider and counterbalancer members at all times, has been illustrated with two rotating pinions, a pair of inner racks, and a pair of outer racks. It will be understood that some variations are possible in the exact numbers and location of racks and pinions.

For example, more than two supporting pinions can be spaced symmetrically around the longitudinal axis of movement of the unit, and corresponding numbers of inner and outer racks can be associated with the respective supporting pinions. Instead of pinions, rotatably supported gear members having inner and outer gear teeth or gear sectors of different radius may also be used in some cases. In such a case, however, the slider and counterbalancer members will move in opposite directions at all times, but not through equal distances on a one-to-one basis. Thus the effective total masses of the respective slider and counterbalancer members, including all parts moving longitudinally along the longitudinal axis as a unit with each such member must be selected for optimum counterbalancing so that the absolute value of the product of the total slider mass times its distance of travel along the axis is equal to the absolute value of the product of the total counterbalancer mass times its distance of travel along the axis in the opposite direction.

The improved counterbalancing and driving mechanism is particularly useful in the design of compressor assemblies which include first and second cylinder wall portions in coaxial alignment with the longitudinal axis of movement of a slider and counterbalancer member, with first and second piston portions providing respective first and second piston faces, and with the relative axial locations of the respective cylinder wall and piston portions and the particular movable slider or counterbalancer member(s) with which each piston portion and piston face moves as a unit providing at least first and second respective compression chambers. In some cases, the arrangement is such that a compression stroke takes place in one chamber during movement of the connecting rod generally longitudinally in one direction, while a compression stroke takes place in the other chamber during movement of the connecting rod generally longitudinally in the opposite direction. The two cylinder wall portions can be longitudinally adjacent to each other as parts of a common cylinder within which the first and second piston portions provide opposite ends of a common compression chamber and are connected respectively to the slider and counterbalancer members. Part of one of the cylinder wall portions can serve as the guide means for the slider. In other cases, the first and second cylinder wall portions can be axially aligned portions of a common cylinder positioned longitudinally between the crankshaft axis and the two rotatably supported gear members of the special interconnecting mechanism. Still other variations in relative axial location and arrangement will be apparent to those skilled in the art on the basis of the teachings herein.

Also, as described herein, the invention is capable of a range of fixed stroke applications in which working members other than compressor piston faces can be used, and in which one or more of such working members can be connected to move as a unit as at least part of any one or more of the respective crankshaft, slider and counterbalancer members, while a power member or a connecting means for a motor member can be associated with another of said crankshaft, slider and counterbalancer members. The use of an improved balancing and interconnecting mechanism, including inner and outer racks and intermediate pinions, to insure opposite straight-line balancing movement of the respective slider and counterbalancer members, offers particular advantages in providing improved counterbalancing of the reciprocating masses of a fixed stroke piston machine along a common longitudinal axis, in combination with a connecting rod and counterbalanced single-throw crankshaft arrangement in which effective practical counterbalancing of undesired centrifugal forces due to rotary movement is also achieved.

The foregoing specification accordingly sets forth some of the ways in which the invention may be practiced, including the best mode presently contemplated for carrying out the invention. Other modifications and variations may be apparent to those skilled in the art, in the light of the foregoing description and the following claims.

We claim:

1. A counterbalanced fixed stroke piston machine comprising a first movable member serving as a slider member, a housing including guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straightline reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, said housing comprising at least a first cylinder wall portion in coaxial alignment with said longitudinal axis, at least a first fixed stroke piston portion, with at least one piston face, movable within said cylinder wall portion and associated with and reciprocating longitudinally as a unit as at least part of one of the slider and counterbalancer members, thereby providing at least part of a first variable volume cylinder chamber within the first cylinder wall portion, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a singlethrow crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism having a symmetrical force transmitting and balancing arrangement including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion having at least two rigidly interconnected inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members.

2. A counterbalanced fixed stroke piston machine according to claim 1 in which the rack portion which reciprocates longitudinally as a unit with the slider member is spaced longitudinally from that part of the slider member which engages the guide means and has a pivotal connection to that part of the slider member for limited pivotal movement on an axis extending crosswise of the longitudinal axis for insuring smooth linear reciprocation of that part of the slider member on the guide means and floating movement of the lastmentioned rack portion and its racks in their engagement with the rotatably supported gear members.

3. A counterbalanced fixed stroke piston machine according to claim 1 in which the mass of the second movable member, including all portions moving longitudinally as a unit therewith, exceeds the mass of the first movable member, including all portions other than the connecting rod moving longitudinally as a unit therewith, by an amount equal to only a portion of the total connecting rod mass, and in which the mass of the counterbalancing portion of the crankshaft exceeds the mass required to counterbalance only the single-throw crank portion by an amount equal to only a portion of the mass required to balance the total connecting rod mass, and in which the rotatably supported gear members are pinions.

4. A counterbalanced fixed stroke piston machine according to claim 1 further comprising a second cylinder wall portion in coaxial alignment with said longitudinal axis, and a second piston portion with a second piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the first and second movable members, the relative axial locations and constructions of the respective cylinder wall and piston portions and the particular movable member with which each piston portion and piston face moves as a unit providing at least first and second variable volume cylinder chambers in the machine.

5, A counterbalanced fixed stroke piston machine according to claim 4 having a first piston portion moving longitudinally as a unit as at least part of said slider member and a second piston portion moving as a unit as at least part of said counterbalancer member.

6. A counterbalanced fixed stroke piston machine according to claim 4, having first and second piston portions moving longitudinally as a unit as at least part of said slider member.

7. A counterbalanced fixed stroke piston machine according to claim 4 having first and second piston portions moving longitudinally as a unit as at least part of said counterbalancer member.

8. A counterbalanced fixed stroke piston machine having an improved counterbalancing and driving mechanism, said piston machine comprising a first movable member serving as a slider member, guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straight-line reciprocating movememt with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and secondmovable members for counterbalancing, stratight-line movement of such members in opposite directions to each other along said axis at all times, at least a first fixed stroke piston portion, with at least one piston face, and a second piston portion, said first and second piston portions being associated with and reciprocating longitudinally as a unit as at least part of the slider member, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a singlethrow crank'portion and a counterbalancing portion thereon, and a connecting'rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, the first and second piston portionsbeing spaced from each other along said longitudinal axis on opposite sides of said singlethrow crank shaft, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending-crosswise of said longitudinal axis and spaced symmetrically.

from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a'unit with one of said first and second movable members, said inner rack portion having at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable'members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting ofa rotary driving connection on said crankshaft member.

9. A counterbalanced fixed stroke piston machine having an improved counterbalancing and driving mechanism said piston machine comprising a first movable member serving as a slider member, guide means supporting the slidermember forstraight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straight-line reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, at

least a first fixed stroke pistonportion, with at least one piston face, and a second piston portion, said first and second piston portions being associated with and reciprocating longitudinally as a unit as at least part of the counterbalancer member, and another piston portion moving longitudinally as a unit as at least part of said slider member, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a singlethrow crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal'axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion having at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members,

said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack' portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting of a rotary driving connection on said crankshaft member.

10. A counterbalanced fixed stroke piston machine constituting a compressor assembly having an improved counterbalancing and driving mechanism, said piston machine comprising a first movable member serving as a slider member, guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straightline reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, said compressor assembly further comprising first and second cylinder wall portions in coaxial alignment with said longitudinal axis, a first fixed stroke piston portion, with at least one piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the slider and counterbalancer members, and a second piston portion with a second piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the first and second movablemembers, the relative axial locations of the respective cylinder wall and piston portions and the particular movable member with which each piston portion and piston face moves as a unit providing at least a first compression chamber and a second compression chamber, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a single-throw crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forcesfrom one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around andoutwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion ahving at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion in eluding a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting of a rotary driving connection on said crankshaft member.

1 l. A compressor according to claim 10 in which the relative axial locations of the respective cylinder wall and piston portions. and the particular movable member with which each piston face moves as a unit, provide at least two compression chambers in one of which a compression stroke takes place during movement of the connecting rod generally longitudinally in one direction, and in the other of which a compression stroke takes place during movement of the connecting rod generally longitudinally in the opposite direction.

12. A compressor according to claim 10 in which the two cylinder wall portions are longitudinally adjacent to each other and constitute parts of a common cylinder within which the first and second piston portions provide opposite ends of a common compression chamber and are connected respectively to the slider and counterbalancer members.

13. An improved compressor according to claim 10 in which the two cylinder wall portions are longitudinally adjacent to each other and the two piston portions are parts of a single stepped piston member.

14. A plural chamber compressor assembly according to claim 10 in which the machine has a body portion and said cylinder wall portions are at fixed locations on the body portion.

15. A plural chamber compressor according to claim 14 in which said guide means is part of one of the cylinder wall portions.

16. A plural chamber compressor according to claim 15 in which one of said piston portions constitutes at least part of said slider member.

17. A compressor according to claim 10 in which the first and second cylinder wall portions are axially aligned portions of a common cylinder, and the common cylinder is positioned longitudinally between the crankshaft axis and the two rotatably supported gear members.

18. A compressor according to claim 10 in which the first and second cylinder wall portions and their respective first and second piston face portions are positioned along said longitudinal axis at opposite sides of said crankshaft axis, with the first and second piston face portions reciprocating as a unit as at least part of the movable slider member, and the two rotatably supported gear members being positioned longitudinally on the opposite side of the crankshaft from the connecting rod. 

1. A counterbalanced fixed stroke piston machine comprising a first movable member serving as a slider member, a housing including guide means supporting the slider member for straightline reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straightline reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for Counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, said housing comprising at least a first cylinder wall portion in coaxial alignment with said longitudinal axis, at least a first fixed stroke piston portion, with at least one piston face, movable within said cylinder wall portion and associated with and reciprocating longitudinally as a unit as at least part of one of the slider and counterbalancer members, thereby providing at least part of a first variable volume cylinder chamber within the first cylinder wall portion, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a single-throw crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism having a symmetrical force transmitting and balancing arrangement including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion having at least two rigidly interconnected inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members.
 2. A counterbalanced fixed stroke piston machine according to claim 1 in which the rack portion which reciprocates longitudinally as a unit with the slider member is spaced longitudinally from that part of the slider member which engages the guide means and has a pivotal connection to that part of the slider member for limited pivotal movement on an axis extending crosswise of the longitudinal axis for insuring smooth linear reciprocation of that part of the slider member on the guide means and floating movement of the last-mentioned rack portion and its racks in their engagement with the rotatably supported gear members.
 3. A counterbalanced fixed stroke piston machine according to claim 1 in which the mass of the second movable member, including all portions moving longitudinally as a unit therewith, exceeds the mass of the first movable member, including all portions other than the connecting rod moving longitudinally as a unit therewith, by an amount equal to only a portion of the total connecting rod mass, and in which the mass of the counterbalancing portion of the crankshaft exceeds the mass required to counterbalance only the single-throw crank portion by an amount equal to only a portion of the mass required to balance the total connecting rod mass, and in which the rotatably supported gear members are pinions.
 4. A counterbalanced fixed stroke piston machine according to claim 1 further comprising a second cylinder wall portion in coaxial alignment with said longitudinAl axis, and a second piston portion with a second piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the first and second movable members, the relative axial locations and constructions of the respective cylinder wall and piston portions and the particular movable member with which each piston portion and piston face moves as a unit providing at least first and second variable volume cylinder chambers in the machine.
 5. A counterbalanced fixed stroke piston machine according to claim 4 having a first piston portion moving longitudinally as a unit as at least part of said slider member and a second piston portion moving as a unit as at least part of said counterbalancer member.
 6. A counterbalanced fixed stroke piston machine according to claim 4, having first and second piston portions moving longitudinally as a unit as at least part of said slider member.
 7. A counterbalanced fixed stroke piston machine according to claim 4 having first and second piston portions moving longitudinally as a unit as at least part of said counterbalancer member.
 8. A counterbalanced fixed stroke piston machine having an improved counterbalancing and driving mechanism, said piston machine comprising a first movable member serving as a slider member, guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straight-line reciprocating movememt with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, stratight-line movement of such members in opposite directions to each other along said axis at all times, at least a first fixed stroke piston portion, with at least one piston face, and a second piston portion, said first and second piston portions being associated with and reciprocating longitudinally as a unit as at least part of the slider member, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a single-throw crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, the first and second piston portions being spaced from each other along said longitudinal axis on opposite sides of said singlethrow crank shaft, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion having at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting of a rotary driving connection on said crankshaft member.
 9. A counterbalanced fixed stroke piston machine having an improved counterbalancing and driving mechanism said piston machine comprising a first movable member serving as a slider member, guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straight-line reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, at least a first fixed stroke piston portion, with at least one piston face, and a second piston portion, said first and second piston portions being associated with and reciprocating longitudinally as a unit as at least part of the counterbalancer member, and another piston portion moving longitudinally as a unit as at least part of said slider member, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a single-throw crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion having at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting of a rotary driving connection on said crankshaft member.
 10. A counterbalanced fixed stroke piston machine constituting a compressor assembly having an improved counterbalancing and driving mechanism, said piston machine comprising a first movable member serving as a slider member, guide means supporting the slider member for straight-line reciprocating movement with its center of gravity moving along a desired longitudinal axis, a second movable member serving as a counterbalancer member also supported for straight-line reciprocating movement with its center of gravity moving along the same longitudinal axis, interconnecting mechanism connecting the first and second movable members for counterbalancing, straight-line movement of such members in opposite directions to each other along said axis at all times, said compressor assembly further comprising first and second cylinder wall portions in coaxial alignment with said longitudinal axis, a first fixed stroke piston portion, with at least one piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the slider and counterbalancer members, and a second piston portion with a second piston face, associated with and reciprocating longitudinally as a unit as at least part of one of the first and second movable members, the relative axial locations of the respective cylinder wall and piston portions and the particular movable member with which each piston portion and piston face moves as a unit providing at least a first compression chamber and a second compression chamber, a counterbalanced single-throw rotary crankshaft member extending generally crosswise with reference to said longitudinal axis and having a single-throw crank portion and a counterbalancing portion thereon, and a connecting rod having one end pivotally connected to said crank portion and a second end pivotally connected to the slider member for transmission of desired forces from one of said rotary crankshaft and reciprocating slider members to the other, said interconnecting mechanism including at least two gear members rotatably supported for rotation on supporting axes extending crosswise of said longitudinal axis and spaced symmetrically from each other around and outwardly from said longitudinal axis, an inner rack portion reciprocating longitudinally as a unit with one of said first and second movable members, said inner rack portion ahving at least two inner racks with teeth projecting outwardly away from each other and respectively engaging the corresponding gear members and guiding the inner rack portion for floating movement along said longitudinal axis between said gear members, and an outer rack portion having at least two outer racks reciprocating longitudinally as a unit with the other of said first and second movable members, said outer racks being spaced outwardly from and parallel to the inner racks and having teeth projecting inwardly and respectively engaging the corresponding gear members, said outer rack portion including a frame member moving as a unit with said outer racks and rigidly interconnecting said outer racks at a location close to said gear members and thereby guiding and supporting the outer racks on said gear members for floating movement along said longitudinal axis, and power means for applying a driving force to one of said crankshaft, slider and counterbalancer members, said power means consisting of a rotary driving connection on said crankshaft member.
 11. A compressor according to claim 10 in which the relative axial locations of the respective cylinder wall and piston portions, and the particular movable member with which each piston face moves as a unit, provide at least two compression chambers in one of which a compression stroke takes place during movement of the connecting rod generally longitudinally in one direction, and in the other of which a compression stroke takes place during movement of the connecting rod generally longitudinally in the opposite direction.
 12. A compressor according to claim 10 in which the two cylinder wall portions are longitudinally adjacent to each other and constitute parts of a common cylinder within which the first and second piston portions provide opposite ends of a common compression chamber and are connected respectively to the slider and counterbalancer members.
 13. An improved compressor according to claim 10 in which the two cylinder wall portions are longitudinally adjacent to each other and the two piston portions are parts of a single stepped piston member.
 14. A plural chamber compressor assembly according to claim 10 in which the machine has a body portion and said cylinder wall portions are at fixed locations on the body portion.
 15. A plural chamber compressor according to claim 14 in which said guide means is part of one of the cylinder wall portions.
 16. A plural chamber compressor according to claim 15 in which one of said piston portions constitutes at least part of sAid slider member.
 17. A compressor according to claim 10 in which the first and second cylinder wall portions are axially aligned portions of a common cylinder, and the common cylinder is positioned longitudinally between the crankshaft axis and the two rotatably supported gear members.
 18. A compressor according to claim 10 in which the first and second cylinder wall portions and their respective first and second piston face portions are positioned along said longitudinal axis at opposite sides of said crankshaft axis, with the first and second piston face portions reciprocating as a unit as at least part of the movable slider member, and the two rotatably supported gear members being positioned longitudinally on the opposite side of the crankshaft from the connecting rod. 